The present invention relates to a sensing head for a measuring machine with straight line guiding systems for the deflection of a measuring sensor in x, y, and z coordinate directions, the first straight line guiding system being attached to a beam member of the measuring machine and each straight line guiding system comprising a beam on which the respective next straight line guiding system is arranged. The measuring sensor is attached on the beam of the third straight line guiding system, and springs are provided for weight compensation.
Such a sensing head is described in U.S. Pat. No. 3,869,799 (German patent application No. 2,242,355). There a spiral spring whose tension is adjustable by means of a motor is arranged between a beam member and a measuring sensor. Thereby the weight which loads the straight line guiding system acting in the z-direction is to be compensated. What is favorable about this arrangement is that the spiral spring influences the characteristics of the straight line guiding systems acting in the x- and y-directions. In addition, this arrangement is costly due to the use of a motor drive.